The present invention is generally directed to mass analyzers. More particularly, the present invention is directed to a mass analyzer that facilitates parallel processing of one or more analytes. In accordance with further aspects of the present invention, various mass filter chamber arrangements that use non-planar electrodes to generate the electric field in a given chamber are also set forth.
The characteristics of mass spectrometry have raised it to an outstanding position among the various analysis methods. It has excellent sensitivity and detection limits and may be used in a wide variety of applications, e.g. atomic physics, reaction physics, reaction kinetics, geochronology, biomedicine, ion-molecule reactions, and determination of thermodynamic parameters (xcex94Gxc2x0f, Ka, etc.). Mass spectrometry technology has thus begun to progress very rapidly as its uses have become more widely recognized. This has led to the development of entirely new instruments and applications.
Development trends have gone in the direction of increasingly complex mass analyzer designs requiring highly specialized components and tight manufacturing tolerances. Longer analysis times are often associated with this increased complexity. This, in turn, requires system designers to make significant design trade-offs between the accuracy of the mass measurements and the time required to obtain those measurements. However, such trade-offs have become increasingly intolerable in the competitive field of drug discovery and analysis. There, mass analyzers must be both highly accurate and provide for a high throughput of analytes.
Several mass analyzer embodiments based on ion separation in the presence of an electric field are illustrated in the figures of U.S. Pat. No. 5,726,448 to Smith et al, the structures of which are hereby incorporated by reference. FIGS. 3-5 of the ""488 patent show a first embodiment of a mass analyzer having a mass filter chamber through which only ions of a selected range of mass-to-charge ratios are permitted to pass. In this embodiment, the mass filter chamber includes first and second electrode pairs that are connected to an RF signal source to generate an electric field therebetween. Each pair of electrodes is formed by an opposed pair of conductive plates. The planar faces of the first electrode pair face each other while the planar faces of the second electrode pair likewise face one another. However, the planar faces of the first electrode pair are disposed substantially perpendicular to the planar faces of the second electrode pair. Both the first and second electrode pairs are aligned along the same length of the chamber.
In a further embodiment, shown in FIG. 10 of the ""488 patent, the second electrode pair is displaced from the first electrode pair along the length of the mass filter chamber. In all other respects, this embodiment is substantially similar to the one shown in FIGS. 3-5.
In each of the foregoing embodiments, the electric field generated at the second electrode pair is out of phase by xcfx80/2 from the electric field generated at the first electrode pair so that the ions are acted upon by at least two distinct, orthogonal electric fields. As predominantly noted in FIG. 3 of the ""488 patent, the orthogonal electric fields are preferably sinusoidal in nature and combine to form a rotating electric field.
In operation, each ion enters the mass selection chamber at angles, xcex8 and "PHgr", with respect to a plane forming the inlet of the chamber. Whether or not the ion passes completely through the mass selection chamber depends on the mass-to-charge ratio of the ion as well as the frequency of the rotating electric field, the amplitude of the rotating electric field, the phase of the electric field at the time that the ion enters the chamber and the entry angles, xcex8 and "PHgr".
The present inventor has recognized that the existing mass analysis apparatus shown in the ""448 patent may be improved in a variety of manners. For example, trade-offs must frequently be made between system throughput and mass resolution/sensitivity when employing existing mass analyzer constructions. Therefore, there is a need for mass analyzer constructions having increased throughput without corresponding sacrifices in manufacturing, mass resolution, and/or mass sensitivity goals. Further, the electrode configuration shown in the ""488 patent generates less than optimal electric field shapes that are particularly undesirable when a device of that type is miniaturized.
An improved mass analyzer capable of parallel processing one or more analytes is set forth. The improved mass analyzer comprises a mass filter unit having a plurality of ion selection chambers disposed in parallel with one another. Each of the plurality of ion selection chambers respectively includes an ion inlet lying in an inlet plane and an ion outlet lying in an outlet plane. The mass analyzer further includes a plurality of electrodes disposed in the ion selection chambers and at least one RF signal generator connected to the plurality of electrodes to produce a rotating electric field in each ion selection chamber. A plurality of ion injectors are each coupled to inject an ion beam into the ion inlet of a respective ion selection chambers. The ions meeting predetermined mass-to-charge (m/Q) ratio requirements pass through the ion selection chambers to contact corresponding detection surfaces of an ion detector and/or ion detector array. The mass filter array may be constructed so that at least one pair of ion selection chambers share at least one common field generating electrode.
Further aspects of the present invention include an improved mass filter that can be used in the foregoing multi-processing configuration or in a single ion selection chamber device. The mass filter comprises at least a first pair of opposed electrodes as well as a second pair of opposed electrodes. Each electrode of the first pair includes a concave electrode surface. The concave electrode surfaces of the opposed electrodes are disposed to face one another. Likewise, the electrodes of the second pair of opposed electrodes have concave electrode surfaces that face one another. The concave electrode surfaces of the second pair opposed electrodes are angularly displaced with respect to the concave electrode surfaces of the first pair of opposed electrodes. At least one RF signal generator is connected to the electrodes of the first and second electrode pairs to generate a rotating electric field between the concave electrode surfaces.